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Although the boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is a devastating pest in the United States and Mexico, its population structure and genetic diversity in Mexico on wild and cultivated cotton hosts (genus Gossypium) is poorly understood. Past studies using morphology, host use, and distribution records suggest that A. grandis grandis comprises three forms with host-associated characteristics: the southeastern form (from domesticated Gossypium hirsutum L., southeastern United States and northeastern Mexico), the thurberia form (from Gossypium thurberi Todaro, Arizona and northwestern Mexico), and the Mexican form (from multiple Gossypium species and other malvaceous plant genera in the remainder of Mexico and Central America). However, the phylogenetic relationships, host preferences, and distributions of these forms are not completely understood. An alternative hypothesis of an eastern and western form of the boll weevil is suggested by the suspected phylogeographic range expansion from an ancestral distribution in the tropics northward along both Mexican coasts, culminating in the maximally contrasting phenotypes observed in the northeastern and northwestern arms of the current distribution. In this study, we sequenced one mitochondrial and four nuclear genes to gain insight into the evolutionary relationships among the putative forms and their distributions on wild and domesticated cotton hosts. Using models of evolution, we compared the three-form to the two-form classification and to two alternative classifications that incorporate geography and host use traits. The genetic data at most loci provide stronger support for the two-form than the three-form hypothesis, with an eastern and western group separated by the Sierra Madre Occidental mountain range. They do not support separate taxonomic status for boll weevils developing on G. thurberi. [ABSTRACT FROM AUTHOR]

An existing microsatellite genotype database has been used for several years in population genetic assignment analyses of boll weevils, Anthonomus grandis grandis Boheman (Coleoptera: Cureulionidae), captured in eradication zones. It is important to update it in case of changes in genotype frequency at any of the locations over time. Such changes at neutral loci could be caused by drift, immigration, or population bottlenecks. We examined allele frequency distribution for 10 microsatellite loci to determine genetic differentiation among 10 boll weevil populations sampled from Texas and Mexico in 2009. In addition, temporal changes in genetic composition were examined in the eight populations for which samples were available from previous years. Substantial levels of spatial genetic structure were observed, with the 10 populations clustering as four major groups. Pairwise FST estimates in 2009 samples ranged from 0.001 (College Station-Cameron) to 0.492 (College Station-Ojinaga). There was little change in genetic profiles over time at four of the eight locations. Thus, for those four locations, genotype and allele frequency data can be pooled over the two sample dates, which will provide greater statistical power in future population assignment tests. However, genetic profiles changed substantially at Ojinaga, and to a lesser extent at Uvalde, Cameron, and Rosales, so the 2009 genotype data should be substituted in future analyses. Finally, populations from two new locations, Brownsville and Lockhart, TX, were sampled, genotyped, and added to the database. The addition of Lockhart is particularly important given its surprisingly high differentiation from the relatively nearby populations of Cameron and Uvalde. [ABSTRACT FROM AUTHOR]